During January-November 1995, a total of 19 laboratory-confirmed cases of wound botulism were reported to the California Department of Health Services (CDHS); of these, 13 had occurred since August. Since 1990, the number of wound botulism cases reported annually in California has increased steadily (one case in 1990, two in 1991, three in 1992, four in 1993, and 11 in 1994). All cases except one since 1991 have occurred in injecting-drug users, and many involved subcutaneous injection or "skin popping" of black tar heroin. This report summarizes the findings of the investigation of two cases.

Case 1.On September 23, a 44-year-old male user of black tar heroin developed an abscess on his right arm, which was treated unsuccessfully with cephelexin and ciprofloxacin; on September 29, the abscess was incised and drained. On October 1, he was examined at a local emergency department (ED) because of slurred speech and was